Rolling of metal stock



Aug. 22, 1961 H. CRAMER ROLLING 0F METAL STOCK Filed April 17, 1957 UTE/7 4 T m em Patented Aug. 22, 1961 2,996,937 ROLLING F METAL STOCK Hans Cramer, Hankerstrasse 3, Eichen, Kreis Siegen, Germany Filed Apr. 17, 1957, Ser. No. 653,487 Claims priority, application Germany Apr. 23, 1956 1 Claim. (Cl. 80-60) This invention relates to new and useful improvements in the rolling of metal stock. The invention more particularly relates to an improved method and mill set-up for hot rolling metal stock in a strip mill provided with a reversing rougher and a continuously operating finish ing mill having several stands.

In the hot rolling strip mills having a reversing rougher and a continuously operating finishing mill consisting of several, as for example six, finishing stands, may be used. In operation, the stock is rolled back and forth in the reversing rougher mill a multiple number of passes. After the last pass through the reversing rougher, the stock is passed to and through the finishing mill. The stands of which are brought close together, so that the length of the finishing mill is much less than the length of the stock being rolled by the finishing mill.

The stand of the reversing rougher has been'positioned a sufficient distance from the first stand of the finishing mill so that the material being rolled passed through and clear of the reversing rougher on its last pass prior to being fed to the first stand of the finishing mill train. The distance between the reversing rougher and the first stand of the finishing train therefore had to be greater than the length of the material being rolled on its longest, i.e., last pass through the reversing rougher. Due to this requirement, the entire mill had to have a large structural length which, in addition to the obvious economic disadvantage, would result in a strong temperature loss and an increase in scaling of the rolled stock. These were the reasons which limit the maximum length of the rolled stock and therefore the maximum coil weight produced.

One object of this invention is a method for operating a hot-rolling strip mill and a strip mill construction which overcomes the above mentioned disadvantages. This, and still further objects, will become apparent from the following description read in conjunction with the drawing which diagrammatically shows an embodiment of a mill in accordance with the invention.

The invention is broadly directed to an improvement for the method of rolling stock in a hot-rolling strip mill having a reversing stand and a finishing train with several stands in which the stock is rolled back and forth in the reversing stand over a number of passes and thereafter passed through the finishing train and to an improvement in the construction of a hot-rolling strip mill of this type.

In accordance with the invention, the first stand of the finishing train is maintained at a distance from the reversing stand less than the length of the stock after its last pass through the reversing stand and the stock on its last pass through the reversing stand is fed into the first stand of the finishing train prior to a complete emergence from the reversing stand and the first stand of the finishing train, while synchronizing the speed of the reversing stand.

The synchronization of the speeds of the reversing stand and the first stand of the finishing train while the stock is simultaneously being passed therethrough, is preferably effected by adjusting the speed of the reversing stand at the end of its last pass as the stock is simultaneously fed into the finishing train to equal the speed of the first stand of the finishing train.

The first stand of the finishing train is preferably maintained at a distance from the reversing stand only a little more than the length of the stock after its third from last pass through the reversing stand.

The mill, in accordance with the invention, as contrasted with the prior art mill, is so constructed that the first stand of the finishing train is positioned to receive the rolled stock directly from the reversing stand on its last pass prior to complete emergence therefrom and means are provided, as for example, means to control the speed of the reversing stand for synchronizing the speed of the reversing stand and the first finishing stand while simultaneously engaging the same piece of rolled stock. The reversing stand and first stand of the finishing train are thus positioned at a distance from each other less than the length of the stock after its final pass and preferably at nearly the distance of the length of the stock after its third from last pass, as for example its fifth pass, when the mill is operated with for instance seven passes in the reversing stand.

The drawing is a plan View of a mill for use with the method disclosed. The finishing train preferably is provided with tour stands as contrasted to the conventional SIX.

Referring to the embodiment shown in the drawing, the hot-rolling strip mill has furnaces 1 for heating the slabs to be rolled, a reversing stand 2 provided with the pressure rollers 2 and a finishing train provided with four stands 3, 4, 5 and 6 and a coiler 7. The rollers of the stands are driven in the conventional manner by conventional drive means 2a, 3a, 4a, 5a, 6a respectively. The speeds of the rollers of the stands 3, 4, 5 and 6 of the continuous finishing train are in a known manner matched so that the stock is rolled continuously and simultaneously by said rollers. The speeds of the rollers of the reversing stand 2 are controlled by means of the control box 8 to the speeds of the rollers of the first stand 3 of the finishing train.

In operation the stock is moved in a conventional way from one of the furnaces: 1 to the reversing stand 2 and is then passed back and forth through the reversing stand 2 over a multiple number of passes, as for example 7 passes. The distance d between the reversing stand 2 and the first stand 3 of the finishing train is so adjusted to be nearly equal to the length of the stock after its third from last, as for example pass, through the reversing stand 2. On each pass through the reversing stand 2, the length of the stock is, of course, increased and in the drawing the stock 9 is shown in a position upon reaching the end of the third from last, as for example the fifth pass. As may be noted, the length of this pass is just sufiicient to reach the first stand 3 of the finishing train without being engaged by the rollers of the stand 3. On the next to last pass in the reverse direction, the length of the stock is increased and in the drawings is shown in dotted lines at 9a, and on the final or last pass the length of the stock is still further increased so that the same is approximately equal to 1.4d. With this additional length near the end of the last pass the stock will be engaged by the rollers of the first stand 3 of the finishing train while still being engaged on the last pass by the reversing stand. At this point, the speed of the rollers of the reversing stand 2 synchronize to that of the rollers of the first stand 3 of the finishing train. This synchronization may be effected, for example, by adjusting the speed of the rollers of the reversing stand 2 by means of the control box 8. The speed of the rollers referred to herein is the peripheral speed and not the revolutionary speed. The stock will then pass directly from the reversing stand 2 through the first stand 3 of the finishing train and through the subsequent stands of the finishing train as shown; the finished stock will than in the conventional Way be coiled up to coils by the coiler 7.

The invention allows a substantial decrease in the length of the mill as a Whole and conversely an increase in the length of the stock which may be rolled in a mill of a given length. If, for example, in accordance with the rolling program for the reversing stand, a thickness of 18 mm. is to be achieved on the last pass, a thickness of 30 mm. on the next to last pass, and a thickness of 45 mm. on the third from last pass, the distance of the reversing stand from the first finishing stand may be shortened in a ratio of 18:45 and therefore about 40% of the distance previously required. By the same token, in a mill of a given length, the rolling length and thus the coil weight may be increased 250% as compared to that obtained in conventional operation.

By dispensing with a shortening of the customary distance between the reversing stand and the first finishing stand, the number of finishing stands may be reduced as for example from the conventional 6 to 4 Without having to reduce the coil weights or to increase the minimum strip thickness Which can be obtained. In such an arrangement, the reversing stand may be operated with seven passes and, as mentioned, the length of the stock after the fifth pass is approximately equal to the distance of the reversing stand from the first finishing stand.

While the invention has been described in detail with reference to certain specific embodiments, various changes and modifications which fall within the spirit of the invention and scope of the appended claim will become apparent to the skilled artisan.

I claim:

In-the method for rolling stock in a strip rolling mill having a reversing stand and a finishing train with several stands in which the stock is rolled back and forth in the reversing stand over a number of passes and thereafter passed through the finishing train, the improvement which comprises maintaining the first stand of the finishing train at a distance from the reversing stand less than the length of the stock after the last pass through the reversing stand, and feeding the stock into the first stand of the finishing train on its last pass through the reversing stand prior to complete emergence from the reversing stand and synchronizing the speed of the reversing stand and the first stand of the finishing train.

References Cited in the file of this patent UNITED STATES PATENTS 1,021,468 McMurtry Mar. 26, 1912 1,736,324 Naugle et a1. Nov. 19, 1929 1,771,688 Nye July 29, 1930 1,895,303 Wilson Jan. 24, 1933 2,322,080 Wickler et al. June 15, 1943 2,332,803 Lorig Oct. 26, 1943 2,770,867 Spencer Nov. 20, 1956 FOREIGN PATENTS 464,513 Great Britain Apr. 19, 1937 505,968 Great Britain May 19, 1939 

